With access of high proportion of new energy to the traction power supply system

the original AC system becomes into an AC-DC hybrid system and

at the same time

the frequency coupling effect between the AC and DC ports exacerbates the risk of system instability

which poses a serious threat to the stable operation of the traction power supply system. In order to solve the problem of system stability due to the frequency coupling effect

in this study an AC/DC three-port impedance model for optical storage access to the traction power supply system is established

the influence of the frequency coupling effect on the system stability is analyzed

and a symmetric phase-locked-loop-based frequency coupling suppression method is proposed. Moreover

the stability differences among the original model

the neglected AC side coupling model and the neglected AC/DC port coupling model are studied and compared. Based on the mechanism of the frequency coupling effect on the system stability

the symmetric phase-locked loop control structure is designed further to suppress the frequency coupling effect caused by the asymmetry of the phase-locked loop section by symmetrizing the d-axis and q-axis voltage control. The simulation experiments by MATLAB/Simulink show that the original system is destabilized due to frequency coupling effect when the same inductance is output from the railway power conditioner (RPC)

and after the frequency coupling suppression is adopted

the output voltage

current

and DC bus voltage remain stable

and the stability boundary of the system is significantly improved

which provides theoretical support and engineering references for the safe access of optical storage to the traction power supply system. It provides theoretical support and engineering reference for the safe access of optical storage to the traction power supply system.